Zircon U-Pb SHRIMP ages of high-pressure granulite in Yushugou ophiolitic terrane in southern Tianshan and their tectonic implications

Zircons from two high-pressure granulite samples from the Yushugou ophiolitic terrane, southern Tianshan have been investigated by cathodoluminescence, LAICPMS and ion microprobe (SHRIMP) for their internal textures, trace elemental compositions and in situ dating. The weighted mean ages of these two samples are 392 ±7 and 390 ±11 Ma, respectively, representing the granulite-facies metamorphic age of the ophiolitic terrane, and indicating that the southern Tianshan ocean initiated its northward subduction since the early Devonian.